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The sensor being the first link of a measuring chain converts a physical measured quantity (e.g. pressure, distance, temperature) into an electrically measurable quantity (e.g. voltage, resistance). This is done by taking advantage of various electrical and / or physical effects.

The following information is provided to support you choosing a suitable sensor. Sensors are not available at bmcm. You will also find a selection of sensor manufacturers we recommend.

Indirect Measurements

You can only measure few quantities directly with DAQ systems (e.g. current, voltage). Therefore physical laws including a current or voltage relation are applied (indirect measurements).

A resistance measurement, for example, is done by connecting a resistor to a constant current source and measuring the voltage drop. The resistance results from the division of the measured voltage through the applied current.

Sensor Adjustment

As you see, sensors "translate" physical into electrical quantities.

To connect them to a measuring system, the output must correspond in unit and range of values with the input of the DAQ device.

Active Sensors

In many sensors, this electronic function is already included and they need their own power supply.

Those sensors are called active sensors, as they convert the measured quantity into a measurable electrical quantity themselves.

Physical Measured Quantities

The following list of sensor types exclusively applies to analog measured quantities, as we focus on analog measurement technology.

Measured Quantity

Physical Phenomenon

Sensor Type

Comments, Examples

temperature

temperature dependance of resistance

PT100, PT1000, NTC, PTC

nonlinear element

temperature

Seebeck effect (thermoelectric voltage)

thermocouple

large measuring range, nonlinear element

temperature

temperature dependance of semiconductors

diodes, transistors

also available as active sensor

temperature

pyroelectric effect

for temperature change only

pressure, tension

piezoelectric effect

piezoelectric element

for force and pressure changes only

pressure, tension, torque moment

resistance dependance of the conductor shape

strain gauge (DMS)

usually connect as measuring bridge

position, length, angle, distance

inductivity change of a coil when inserting a metal piece LVDT

LVDT, differential choke

measurement with carrier frequency procedure

position, length, angle, distance

binary encoded angle and distance sensors

angle encoder

incremental or absolute; output digital

angle, distance

linear potentiometer, rotary encoder

potentiometer

analog output signal

magnetic induction

echo voltage with constant current

echo sensor

available as active integrated wiring

acceleration, velocity

tension of metal plates in semiconductor component

semicond. strain gauge

uni- or multidimensional sensor

acceleration, velocity

piezoelectric effect with a seismic mass

piezoelectric element

e.g. airbag sensor

luminous intensity

photonic stimulation of semiconductors

photodiode, phototransistor

available as passive and active sensors

luminous intensity

change of self-conductivity

photoresistor

current

voltage drop at a resistor

shunt

galvanic connection to the meas. current

current

measurement of the Hall

echo sensor

el.isolated from the meas. current

humidity

semiconductors, capacitive sensors

passive elements

sound, sound level

electrodynamic and capacitive microphones

microphones

filling-level

capacitive and optical measurement

active sensors

rotational speed

optical and inductive processes

speed encoder

digital and analog sensors

motion

optical and inductive processes

motion detector

Sensor Manufacturers

The following table provides a small selection of sensor manufacturers. This is just a selection and does not imply any judgement.

Please note that we are not responsible for the contents of the linked sites and we do not check them regularly. In many cases, the mentioned semiconductor manufacturers do not have their own sales department.